In the manufacture of aminophenoldisulfonic acids which are intermediates in the dye industry.
Phenoldisulfonic acid is obtained by hydrolysis of the dichloride with ethyl alcohol and/or water. Nitration and reduction of this acid gives 5- amino-4-hydroxy-1,3-benzenedisulfonic acid. 4-Hydroxy-1,3-benzenedisulfonic acid accelerates the rearrangement of cumene hydroperoxide in the Hock – Lang phenol process.
Crystallise the acid from EtOH/diethyl ether. [Beilstein 11 H 250, 11 I 58, 11 II 139, 6 III 522.]
